[PATCH 5.10 707/717] tracing: Disable ftrace selftests when any tracer is running

Greg Kroah-Hartman
2020-12-28T14:37:11Z

From: Masami Hiramatsu <mhiramat@kernel.org>

commit 60efe21e5976d3d4170a8190ca76a271d6419754 upstream.

Disable ftrace selftests when any tracer (kernel command line options
like ftrace=, trace_events=, kprobe_events=, and boot-time tracing)
starts running because selftest can disturb it.

Currently ftrace= and trace_events= are checked, but kprobe_events
has a different flag, and boot-time tracing didn't checked. This unifies
the disabled flag and all of those boot-time tracing features sets
the flag.

This also fixes warnings on kprobe-event selftest
(CONFIG_FTRACE_STARTUP_TEST=y and CONFIG_KPROBE_EVENTS=y) with boot-time
tracing (ftrace.event.kprobes.EVENT.probes) like below;

[ 59.803496] trace_kprobe: Testing kprobe tracing:
[ 59.804258] ------------[ cut here ]------------
[ 59.805682] WARNING: CPU: 3 PID: 1 at kernel/trace/trace_kprobe.c:1987 kprobe_trace_self_tests_ib
[ 59.806944] Modules linked in:
[ 59.807335] CPU: 3 PID: 1 Comm: swapper/0 Not tainted 5.10.0-rc7+ #172
[ 59.808029] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/204
[ 59.808999] RIP: 0010:kprobe_trace_self_tests_init+0x5f/0x42b
[ 59.809696] Code: e8 03 00 00 48 c7 c7 30 8e 07 82 e8 6d 3c 46 ff 48 c7 c6 00 b2 1a 81 48 c7 c7 7
[ 59.812439] RSP: 0018:ffffc90000013e78 EFLAGS: 00010282
[ 59.813038] RAX: 00000000ffffffef RBX: 0000000000000000 RCX: 0000000000049443
[ 59.813780] RDX: 0000000000049403 RSI: 0000000000049403 RDI: 000000000002deb0
[ 59.814589] RBP: ffffc90000013e90 R08: 0000000000000001 R09: 0000000000000001
[ 59.815349] R10: 0000000000000001 R11: 0000000000000000 R12: 00000000ffffffef
[ 59.816138] R13: ffff888004613d80 R14: ffffffff82696940 R15: ffff888004429138
[ 59.816877] FS: 0000000000000000(0000) GS:ffff88807dcc0000(0000) knlGS:0000000000000000
[ 59.817772] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 59.818395] CR2: 0000000001a8dd38 CR3: 0000000002222000 CR4: 00000000000006a0
[ 59.819144] Call Trace:
[ 59.819469] ? init_kprobe_trace+0x6b/0x6b
[ 59.819948] do_one_initcall+0x5f/0x300
[ 59.820392] ? rcu_read_lock_sched_held+0x4f/0x80
[ 59.820916] kernel_init_freeable+0x22a/0x271
[ 59.821416] ? rest_init+0x241/0x241
[ 59.821841] kernel_init+0xe/0x10f
[ 59.822251] ret_from_fork+0x22/0x30
[ 59.822683] irq event stamp: 16403349
[ 59.823121] hardirqs last enabled at (16403359): [<ffffffff810db81e>] console_unlock+0x48e/0x580
[ 59.824074] hardirqs last disabled at (16403368): [<ffffffff810db786>] console_unlock+0x3f6/0x580
[ 59.825036] softirqs last enabled at (16403200): [<ffffffff81c0033a>] __do_softirq+0x33a/0x484
[ 59.825982] softirqs last disabled at (16403087): [<ffffffff81a00f02>] asm_call_irq_on_stack+0x10
[ 59.827034] ---[ end trace 200c544775cdfeb3 ]---
[ 59.827635] trace_kprobe: error on probing function entry.

Link: https://lkml.kernel.org/r/160741764955.3448999.3347769358299456915.stgit@devnote2

Fixes: 4d655281eb1b ("tracing/boot Add kprobe event support")
Cc: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
kernel/trace/trace.c | 19 +++++++++++++------
kernel/trace/trace.h | 5 +++++
kernel/trace/trace_boot.c | 2 ++
kernel/trace/trace_events.c | 2 +-
kernel/trace/trace_kprobe.c | 9 +++------
kernel/trace/trace_selftest.c | 2 +-
6 files changed, 25 insertions(+), 14 deletions(-)

--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -68,10 +68,21 @@ bool ring_buffer_expanded;
static bool __read_mostly tracing_selftest_running;

/*
- * If a tracer is running, we do not want to run SELFTEST.
+ * If boot-time tracing including tracers/events via kernel cmdline
+ * is running, we do not want to run SELFTEST.
*/
bool __read_mostly tracing_selftest_disabled;

+#ifdef CONFIG_FTRACE_STARTUP_TEST
+void __init disable_tracing_selftest(const char *reason)
+{
+ if (!tracing_selftest_disabled) {
+ tracing_selftest_disabled = true;
+ pr_info("Ftrace startup test is disabled due to %s\n", reason);
+ }
+}
+#endif
+
/* Pipe tracepoints to printk */
struct trace_iterator *tracepoint_print_iter;
int tracepoint_printk;
@@ -2113,11 +2124,7 @@ int __init register_tracer(struct tracer
apply_trace_boot_options();

/* disable other selftests, since this will break it. */
- tracing_selftest_disabled = true;
-#ifdef CONFIG_FTRACE_STARTUP_TEST
- printk(KERN_INFO "Disabling FTRACE selftests due to running tracer '%s'\n",
- type->name);
-#endif
+ disable_tracing_selftest("running a tracer");

out_unlock:
return ret;
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -896,6 +896,8 @@ extern bool ring_buffer_expanded;
extern bool tracing_selftest_disabled;

#ifdef CONFIG_FTRACE_STARTUP_TEST
+extern void __init disable_tracing_selftest(const char *reason);
+
extern int trace_selftest_startup_function(struct tracer *trace,
struct trace_array *tr);
extern int trace_selftest_startup_function_graph(struct tracer *trace,
@@ -919,6 +921,9 @@ extern int trace_selftest_startup_branch
*/
#define __tracer_data __refdata
#else
+static inline void __init disable_tracing_selftest(const char *reason)
+{
+}
/* Tracers are seldom changed. Optimize when selftests are disabled. */
#define __tracer_data __read_mostly
#endif /* CONFIG_FTRACE_STARTUP_TEST */
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -344,6 +344,8 @@ static int __init trace_boot_init(void)
trace_boot_init_one_instance(tr, trace_node);
trace_boot_init_instances(trace_node);

+ disable_tracing_selftest("running boot-time tracing");
+
return 0;
}
/*
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -3201,7 +3201,7 @@ static __init int setup_trace_event(char
{
strlcpy(bootup_event_buf, str, COMMAND_LINE_SIZE);
ring_buffer_expanded = true;
- tracing_selftest_disabled = true;
+ disable_tracing_selftest("running event tracing");

return 1;
}
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -25,11 +25,12 @@

/* Kprobe early definition from command line */
static char kprobe_boot_events_buf[COMMAND_LINE_SIZE] __initdata;
-static bool kprobe_boot_events_enabled __initdata;

static int __init set_kprobe_boot_events(char *str)
{
strlcpy(kprobe_boot_events_buf, str, COMMAND_LINE_SIZE);
+ disable_tracing_selftest("running kprobe events");
+
return 0;
}
__setup("kprobe_event=", set_kprobe_boot_events);
@@ -1887,8 +1888,6 @@ static __init void setup_boot_kprobe_eve
ret = trace_run_command(cmd, create_or_delete_trace_kprobe);
if (ret)
pr_warn("Failed to add event(%d): %s\n", ret, cmd);
- else
- kprobe_boot_events_enabled = true;

cmd = p;
}
@@ -1973,10 +1972,8 @@ static __init int kprobe_trace_self_test
if (tracing_is_disabled())
return -ENODEV;

- if (kprobe_boot_events_enabled) {
- pr_info("Skipping kprobe tests due to kprobe_event on cmdline\n");
+ if (tracing_selftest_disabled)
return 0;
- }

target = kprobe_trace_selftest_target;

--- a/kernel/trace/trace_selftest.c
+++ b/kernel/trace/trace_selftest.c
@@ -787,7 +787,7 @@ trace_selftest_startup_function_graph(st

/* Have we just recovered from a hang? */
if (graph_hang_thresh > GRAPH_MAX_FUNC_TEST) {
- tracing_selftest_disabled = true;
+ disable_tracing_selftest("recovering from a hang");
ret = -1;
goto out;
}